OAKLAND, CA - AUGUST 03: Passengers wait for luggage at Oakland International Airport on August 3, 2011 in Oakland, California. U.S. President Barack Obama is urging members of Congress to pass legislation to end the FAA shutdown by the end of the week. The shutdown has left an estimated 4,000 FAA employees furloughed and nearly 30,000 construction workers out of a job as airport construction projects are stalled. (Photo by Justin Sullivan/Getty Images)

Airlines now have to refund baggage fees on lost bags, pay more cash to passengers involuntarily bumped from oversold flights, and prominently display on their websites fees for checked bags, meals, seat upgrades and other optional services, thanks to new U.S. Department of Transportation rules that took effect Tuesday.

The rules also impose steep penalties on carriers that force passengers on international flights to sit on the tarmac at U.S. airports for more than four hours. Similar rules took effect last year for three-hour tarmac delays on domestic flights.

Although the new rules are a plus for consumers, they "won't change the travel experience for the vast majority of passengers," says Gary Leff, co-founder of Milepoint.com.

Most of the attention has focused on the new higher bump payments, but they apply only to people denied boarding because the plane was overbooked - not to passengers affected by canceled, delayed or diverted flights, says Ed Perkins, contributing editor to SmarterTravel.com.

Such bumps are rare: Not quite 1 out of 10,000 people were involuntarily bumped from overbooked flights in the first half of 2011, according to the Air Transport Association.

The new rules don't apply to people who volunteer to take a later flight in exchange for something - usually travel vouchers - but volunteers might be able to negotiate a better deal now that involuntary-bump payments have gone up, says Jon Fox, a consumer advocate with the California Public Interest Research Group.

Cash payments

Under the new rules, people who are bumped involuntarily will get a cash payment equal to:

-- Double the one-way price of their ticket, up to $650, if they get to their destination within one to two hours of their original arrival time for domestic flights and within one to four hours for international flights.

-- Four times the one-way value of their tickets, up to $1,300, if they arrive more than two hours late for domestic flights and four hours for international flights.

Under the old rules, bump victims got the one-way value of their tickets, up to $400, for the shorter delays and twice the one-way price, up to $800, for longer delays.

If you are on a connecting flight, the mandatory payment applies only to the segment from which you get bumped. For example, if you are flying from San Francisco to New York via Chicago and get bumped from the Chicago-New York leg, the airline can prorate your bump payment based on the fare from Chicago to New York, the Transportation Department says.

Perkins says the only potential downside in the new rules is if airlines cancel more international flights, which often leave only once per day, to avoid the steep tarmac penalties. That was the fear when the tarmac rules on domestic flights took effect last year.

Eliminating delays

Transportation Secretary Ray LaHood says the steep penalties, up to $27,500 per passenger, "virtually eliminated" lengthy tarmac delays on domestic flights. But it's not clear whether they have caused more flight cancellations.

In his blog, LaHood says, "the number of flights canceled after tarmac delays of more than two hours - the flights that could have conceivably been canceled to avoid violating the rule - increased only slightly" since the rule took effect.

But Jenkins says that's because airlines worried about penalties are not waiting two hours to cancel flights, they are canceling a lot more flights after 90 minutes to make sure they have time to get back to the gate, where another plane may be sitting.

Starting Jan. 24, airlines will have to provide additional passenger rights and protections, such as letting passengers hold a reservation without payment, or cancel it without penalty, for 24 hours after the reservation is made if it's placed at least one week before departure. Many airlines already provide this service.

They will also have to include all taxes and mandatory fees in advertised fares, disclose baggage fees when passengers book flights and on e-ticket confirmations, and provide prompt notification of delays of more than 30 minutes, as well as cancellations and diversions.

Airline complaints

In response to my blog post on this subject Tuesday, two readers who were bumped from foreign-bound flights that were canceled and believed they were under-compensated for their lengthy delays wanted to know where they could complain (in addition to the airlines). Neither situation was covered by Department of Transportation rules.

In such cases, passengers need to read the airline's "contract of carriage and see what it says about irregular operations and cancellations," Perkins says. Airlines post these contracts on their websites and also must make them available at the airport.

If the airline violated this binding document, passengers can file a case in small claims court. This may be a lot of trouble, but it could get the attention of the airline's attorneys, Perkins adds.

"On the other hand, if the document says their only responsibility is to get you to the destination on their next flight or they (get you there) or refund the ticket, then you probably don't have a leg to stand on," he says.

Complaining to feds

Perkins notes that airlines typically state they are not responsible for "consequent damage" caused by delays, such as the cost of a missed cruise.